The “A traction Stress Sensor Array for Use in High-Resolution Robotic Tactil Imaging” document by B. J. Kane et al., Journal of Microelectromechanical Systems, vol. 9.4, 2000, describes a device for touch-sensitive characterisation of a surface texture comprising a force sensor coated with a parallelepiped layer composed of a soft elastomer (40 Shore A). This elastomer layer can protect the sensor mechanically while transmitting relief perceived during a surface exploration to it.
One particular disadvantage of such a device is that the contact area between the studied test piece and the coating layer of the sensor is badly determined and is highly dependent on the roughness of the test piece. Thus, it is difficult to make a precise analysis of the texture of the explored surface. Furthermore, wear of this coating creates problems for the reproducibility of measurements during time and it is not easy to replace it when it becomes worn.
The “The Role of Fingerprints in the Coding of Tactile Information Probed with a Biomimetic Sensor” document by J. Scheibert et al., Science Report, Jan. 29, 2009, discloses a coating of a hemi-spherical shaped three-axis force sensor in a device for touch-sensitive characterisation of a surface texture. Although the contact area between the device and a test piece is determined more easily than with the device mentioned above, this device does not solve all problems related to wear of the coating layer during characterisation of the texture of a surface of this test piece, because large changes in the contact area between the test piece and the coating occur after the device has been used several times, due to the large radius of curvature of this coating.